Silver halide emulsions containing 2-pyrazolon-5-one photographic colour couplers

ABSTRACT

Novel magenta forming colour couplers for use in silver halide colour photography are described which correspond to the formula: ##EQU1## wherein R 1  represents hydrogen, alkyl or aryl; R 2  represents fluoroalkyl, cyanoalkyl or phenyl; X is hydrogen or a displaceable group; Ar represents phenylene and Y represents alkyl, aryl, alkylamino, arylamino or alkylarylamino.

The present invention relates to 2-pyrazolon-5-one colour couplers, tothe preparation thereof, to photographic silver halide elements anddeveloping compositions containing such colour couplers as well as tocolour development processes wherein said colour couplers take part inthe formation of a magenta dye image.

It is known that for the formation of a photographic colour image in alight-sensitive silver halide emulsion layer the exposed silver halideis developed by means of an aromatic primary amino colour developer inthe presence of a colour coupler which by reaction with the oxidizeddeveloper forms a dye on the areas corresponding to the silver image.

In subtractive three-colour photography it is common practice to use aphotographic element comprising at least one red-sensitized,green-sensitized and blue-sensitive silver halide emulsion layer,wherein upon development in the presence of suitable colour couplers,cyan, magenta and yellow dye images are formed respectively.

It is desirable that colour couplers employed in colour photography havegood coupling activity, and produce dye images that have the desiredspectral absorption characteristics and favourable stability againstlight, heat and moisture.

Colour couplers may be of the diffusible type or of the non-diffusibletype. By diffusible couplers is meant colour couplers the dispersabilityor solubility of which is sufficient to enable them to be usefullyincorporated in aqueous colour developing solutions whereas bynon-diffusible colour couplers is meant colour couplers intended for usein the photographic element where they should remain during colourdevelopment. Non-diffusible colour couplers are usually obtained byproviding in the colour coupler molecule one or more ballasting groupswhich are sufficiently large to prevent diffusion of the colour couplere.g. aliphatic groups of 5 to 20 C-atoms.

It is known that for homogeneously distributing non-diffusible colourcouplers in a hydrophilic colloid layer, more particularly a silverhalide emulsion layer, special techniques are to be used. Colourcouplers containing a water-solubilizing group e.g. a sulpho group canbe incorporated in the hydrophilic colloid compositions from alkalinesolutions if necessary in the presence of a water-miscible solvent e.g.ethanol. Water-insoluble or sparingly water-soluble colour couplers canbe incorporated in hydrophillic colloid compositions by dispersingtechniques using high-boiling water-immiscible solvents e.g. tricresylphosphate and dibutylphthalate and/or low boiling water-immisciblesolvents e.g. methylene chloride, ethyl acetate, diethyl carbonate, etc.No matter what technique is used, the colour couplers should behomogeneously distributed in the hydrophilic colloid layer and have highstability against crystallization so that colour image formation is notimpaired.

For the formation of the magenta separation image it is known to use2-pyrazolin-5-one colour couplers. In U.S. Pat. Nos. 3,462,270,3,563,745 and 3,567,449 2-pyrazolin-5-one colour couplers carrying inthe 1-position a fluoroalkyl, a β-cyanoalkyl or a benzyl grouprespectively have been described. Though these 1-substituted2-pyrazolin-5-one colour couplers are generally satisfactory it isdesirable to improve the spectral absorption characteristics of the dyesformed upon colour development. It is also desirable to improve theability of the non-diffusible types for being incorporated inhydrophilic colloid media by means of dispersion techniques.

In accordance with the present invention novel 2-pyrazolin-5-one colourcouplers carrying in the 1-position a fluoroalkyl, β-cyanoalkyl orbenzyl group are provided which yield upon colour development azomethinedyes having favourable sensitometric and spectral properties with hightransmission for blue and red light and favourable stability againstlight, heat and moisture. Moreover, the non-diffusible types of thecolour couplers of the present invention lend themselves very well forbeing incorporated in hydrophilic colloid compositions, moreparticularly a silver halide emulsion, by means of dispersion techniquesand stable, finely divided dispersions of the colour couplers in theemulsion layers can be obtained in this way.

The novel colour couplers of the present invention can be represented bythe formula : ##EQU2## wherein :

R₁ represents hydrogen, alkyl e.g. lower alkyl such as methyl or aryle.g. phenyl,

R₂ represents a fluoroalkyl group X(CF₂)_(n=) with X = H or F and n = 1to 10, an α-cyanoalkyl group e.g. cyanomethyl, α-cyanoethyl and α,γ-dicyanopropyl or a phenyl group preferably a phenyl group with one ormore electron-withdrawing substituents e.g. a halogen atom e.g.chlorine, a cyano group, a trifluoromethyl group, an alkylsulphonylgroup e.g. methylsulphonyl, a sulphamoyl group, etc.,

X represents hydrogen or a substituent that exhibits two-equivalentcharacter on colour development e.g. a halogen atom e.g. chlorine atom,an alkylthio, arylthio, or heterocyclic thio group, an alkoxy, aryloxyor acyloxy group, a sulpho group or an arylazo group,

Ar represents phenylene including substituted phenylene e.g. phenylenesubstituted with halogen e.g. chlorine or alkoxy e.g. methoxy, and

Y represents alkyl, aryl, monoalkylamino, monoarylamino, dialkylamino oralkylarylamino.

The term "two-equivalent character" as applied to colour couplingsystems is well known and is described for example in "The theory of thephotographic process" C.E.K. Mees, the Mac-Millan Company, N.Y., 1966,p. 390. It means that by the presence of the splittable substituent onthe active methylene group only two equivalents of silver are needed forthe formation of the dye contrary to four equivalents when the methylenegroup is not substituted.

The colour couplers of the present invention may be of the diffusible ornon-diffusible type as described above.

The invention is particularly concerned with non-diffusible colourcouplers for use in the photographic colour element itself. For thispurpose it is preferred that the group Y in the above general formula isor comprises a ballasting aliphatic straight-chain or branched-chainhydrocarbon group of at least 5 C-atoms. The non-diffusible colourcouplers of the invention lend themselves very well for beingincorporated in the silver halide emulsion by dispersion techniques.

The present invention provides besides novel 2-pyrazolin-5-onecompounds, a method of producing a magenta coloured photographic imagein a photographic light-sensitive silver halide material which comprisesexposing the material and developing it with an aromatic primary aminocolour developing agent in the presence of a 2-pyrazolin-5-one colourcoupler as defined above.

The present invention further provides a photographic element containingat least one silver halide emulsion layer and a 2-pyrazolin-5-one colourcoupler as defined above wherein the group Y is or comprises analiphatic hydrocarbon group of at least 5 C-atoms.

The colour couplers of the present invention can be prepared accordingto methods well known in the art. For example, they can be prepared byreaction of the fluoroalkyl, β-cyanoalkyl and benzyl hydrazines knownfrom the above U.S. Patents with an appropriately substituted anilineand ethyl β, β, β-trimethoxypropionate according to the method describedin the published German patent application No. 2,042,920.

The anilines carrying N-substituted sulphamoyl groups can be prepared bymeans of one of the following procedures :

1. reaction of a nitrobenzene sulphochloride with a primary or secondaryamine in methylene chloride using sodium hydroxide as hydrogen chlorideacceptor, followed by catalytic hydrogenation of the nitro compoundformed, and

2. reaction of an acetylamino benzene sulphochloride with a primary orsecondary amine in methylene chloride using sodium hydroxide as hydrogenchloride acceptor, followed by deacetylation.

The anilines carrying alkyl- or arylsulphonyl groups can e.g. beprepared by the following procedure :

3. alkylation or arylation of an appropriate thioacetanilide followed byoxidation and deacetylation.

Representative anilines prepared according to one of the aboveprocedures and useful for the preparation of the colour couplers of thepresent invention are listed in the following table I.

                                      Table 1                                     __________________________________________________________________________             Amine                            Proce-                                                                            Melting                                                                   dure                                                                              point                                                                         °C                       __________________________________________________________________________                                              1   67                                                                        1   oily                                                                          liquid                                                                    1   39                                                                        1   69                                                                        1   73                                                                        1   85                                                                        3   119                                                                       1   62                                                                        1   72                                                                        1   70                                                                        2   80                              __________________________________________________________________________

The following preparations illustrate how the colour couplers of thepresent invention can be prepared. Representative examples of colourcouplers are listed in table II hereinafter.

PREPARATION 1 : COLOUR COUPLER 2 OF TABLE II

123 g (0.3 mole) of amine 1 of table I in 300 ml of acetic acid and 86.4g (0.36 mole) of ethyl β,β,β-trimethoxy propionate (for 80 % pure) werestirred for 90 min.

The excess of acetic acid and propionate was removed by evaporationunder reduced pressure (1 mm Hg) at 100°-110°C.

57 g (0.3 mole) of α-trifluoromethyl benzylhydrazine and 2 ml of aceticacid were added to the residue. The reaction mixture was stirred for 90min. at 100°-110°C whereupon it was concentrated by evaporation untildry. The residue was recrystallized from 525 ml of methanol.

Yield : 93.5 g (48 %). Melting point : 101°-102°C.

PREPARATION 2 : COLOUR COUPLER 11 OF TABLE II

47.2 g (0.1 mole) of amine 4 of table I and 0.12 mole of ethylβ,β,β-trimethoxypropionate were allowed to react in 100 ml of aceticacid as described in preparation 1.

After evaporation, 11.4 g (0.1 mole) of 2,2,2-trifluoroethylhydrazineand 1 ml of acetic acid were added. The reaction mixture was heated for90 min. at 100- 110°C. It became solid and was recrystallized from 150ml of acetic acid.

Yield : 41.5 g (65 %). Melting point : 138°C.

PREPARATION 3 : COLOUR COUPLER 12 OF TABLE II

This coupler was prepared from 41 g (0.1 mole) of amine 5 of table I,100 ml of acetic acid, 0.12 mole of ethyl β,β,β-trimethoxypropionate and19.1 g (0.1 mole) of 3,4-dichlorobenzyl hydrazine, according to theprocedure of preparation 1. The residue was recrystallized first fromethanol and then from methyl acetate.

Yield : 42.5 g (65.3 %). Melting point : 110°C.

PREPARATION 4 : COLOUR COUPLER 16 OF TABLE II

89.9 g (0.2 mole) of amine 8 of table I and 0.24 mole of ethylβ,β,β-trimethoxypropionate were allowed to react in 200 ml of aceticacid as described in preparation 1.

After evaporation, 200 ml of acetic acid and 38 g (0.2 mole) ofα-trifluoromethyl benzylhydrazine were added. The temperature was keptat 20°C for 5 hours.

After standing overnight, the precipitate formed was filtered by suctionand recrystallized from 275 ml of acetonitrile.

Yield : 80 g (58.6 %). Melting point : 93°C.

                                      Table II                                    __________________________________________________________________________    Colour                                                                             Substituent in       Mel- Yield                                          coup-                     ting %                                              ler   1-position   3-position                                                                           point                                                                  derived from                                                                         °C                                           __________________________________________________________________________    1    --CH.sub.2 CF.sub.3                                                                          amine 5                                                                             135  27.8                                           2                   amine 1                                                                             102  48                                             3    --CH.sub.2 CF.sub.3                                                                          amine 7                                                                             138  52.5                                           4                   amine 5                                                                              101-                                                                              37                                                                       103                                                 5    idem           amine 3                                                                             106  20                                             6    idem           amine 2                                                                              90  40                                             7    idem           amine 7                                                                             149  27.5                                           8                   amine 1                                                                              117-                                                                              37.5                                                                     118                                                 9    --CH.sub.2 CF.sub.3                                                                          amine 1                                                                             106  37.5                                           10                  amine 1                                                                              98  50                                             11   --CH.sub.2 CF.sub.3                                                                          amine 4                                                                             138  65                                             12                  amine 5                                                                             110  65.5                                           13   --CH.sub.2 CF.sub.3                                                                          amine 6                                                                             153  66                                             14                  amine 8                                                                             109  47                                             15   --CH.sub.2 CF.sub.3                                                                          amine 8                                                                              75  56                                             16                  amine 8                                                                              93  58.6                                           17   --CH.sub.2 CF.sub.3                                                                          amine 9                                                                             124  60.5                                           18                  amine 9                                                                              128-                                                                              20                                                                       129                                                 19   --CH.sub.2 CF.sub.3                                                                          amine 10                                                                            160  50                                             20                  amine 10                                                                            142  30                                             21   --CH.sub.2 CF.sub.3                                                                          amine 11                                                                            160  50                                             22                  amine 11                                                                            174  35                                             __________________________________________________________________________

The non-diffusible colour couplers according to the present inventioncan be incorporated into the photographic silver halide elementaccording to any suitable technique known in the art. The colourcouplers of the invention are preferably incorporated into photographichydrophilic colloid media from solutions in high boiling sparinglywater-miscible solvents such as di-n-butyl phthalate and tricresylphosphate or in low-boiling sparingly water-miscible solvents such asethyl acetate, methylene chloride, diethyl carbonate, chloroform, etc.or mixtures thereof in that they have a high solubility therein and veryfine dispersions can be obtained by means of these solvents.

For this purpose these solutions can be dispersed in extremely finedroplets, preferably in the presence of one or more wetting ordispersing agents into a hydrophilic colloid medium e.g. aqueous gelatinor into water, the low-boiling sparingly water-miscible solvent thenbeing removed by evaporation. The stable dispersions of the colourcouplers can be stored as such and then admixed whenever desired withcoating composition itself of the hydrophilic colloid layer such as asilver halide emulsion layer into which the compounds are intended to bepresent.

Of course the compounds of the invention can also be incorporated intothe hydrophilic colloid media in other ways.

More details about particularly suitable techniques that may be employedfor incorporating the colour couplers of the invention into ahydrophilic colloid layer of a photographic material there can bereferred to e.g. U.S. patent specification Nos. 2,269,158, 2,284,887,2,304,939, 2,304,940 and 2,322,027; U.K. patent specification Nos.791,219, 1,098,594, 1,099,414, 1,099,415, 1,099,416, 1,099,417,1,218,190, 1,272,561 and 1,297,347; French patent specification No.1,555,663; Belgian patent specification No. 722,026; German patentspecification No. 1,127,714 and to U.K. patent specification No.1,297,947.

The couplers according to the invention may be used in conjunction withvarious kinds of photographic emulsions. Various silver salts may beused as the sensitive salt such as silver bromide, silver iodide, silverchloride or mixed silver halides such as silver chlorobromide, silverbromoiodide and silver chlorobromoiodide. The couplers can be used inemulsions of the mixed packet type as described in U.S. patentspecification No. 2,698,794 or emulsions of the mixed grain type asdescribed in U.S. patent specification No. 2,592,243. The colourcouplers can be used with emulsions wherein latent images are formedpredominantly on the surface of the silver halide crystal, or withemulsions wherein latent images are formed predominantly inside thesilver halide crystal.

The hydrophilic colloid used as the vehicle for the silver halide maybe, for example, gelatin, colloidal albumin, zein, casein, a cellulosederivative, a synthetic hydrophilic colloid such as polyvinyl alcohol,poly-N-vinyl pyrrolidone, etc. If desired, compatible mixtures of two ormore of these colloids may be employed for dispersing the silver halide.

The light-sensitive silver halide emulsions of use in the preparation ofa photographic material according to the present invention may bechemically as well as optically sensitized. They may be chemicallysensitized by effecting the ripening in the presence of small amounts ofsulphur containing compounds such as allyl thiocyanate, allyl thiourea,sodium thiosulphate, etc. The emulsions may also be sensitized by meansof reductors for instance tin compounds as described in French patentspecification No. 1,146,955 and in Belgian patent specification No.568,687, imino-amino methane sulphinic acid compounds as described inU.K. patent specification No. 789,823 and small amounts of noble metalcompounds such as gold, platinum, palladium, iridium, ruthenium andrhodium compounds. They may be optically sensitized by means of cyanineand merocyanine dyes.

The said emulsions may also comprise compounds which sensitize theemulsions by development acceleration for example compounds of thepolyoxyalkylene type such as alkylene oxide condensation products asdescribed among others in U.S. patent specification Nos. 2,531,832,2,533,990, 3,210,191 and 3,158,484; in U.K. patent specification Nos.920,637 and 991,608 and in Belgian patent specification No. 648,710 andonium derivatives of amino-N-oxides as described in U.K. patentspecification No. 1,121,696.

Further, the emulsions may comprise stabilizers e.g. heterocyclicnitrogen-containing thioxo compounds such as benzothiazoline-2-thioneand 1-phenyl-2-tetrazoline-5-thione and compounds of thehydroxytriazolopyrimidine type. They can also be stabilized with mercurycompounds such as the mercury compounds described in Belgian patentspecification Nos. 524,121, 677,337 and 707,386 and in U.S. patentspecification No. 3,179,520.

The light-sensitive emulsions may also comprise all other kinds ofingredients such as plasticizers, hardening agents, wetting agents, etc.

The non-diffusing magenta colour formers described in the presentinvention are usually incorporated into the green-sensitized silverhalide emulsion for forming one of the differently sensitized silverhalide emulsion layers of a photographic multilayer colour material.Such photographic multilayer colour material usually comprises asupport, a red-sensitized silver halide emulsion layer with a cyancolour former, a green-sensitized silver halide emulsion layer with amagenta colour former and a blue-sensitive silver halide emulsion layerwith a yellow colour former.

The emulsions can be coated on a wide variety of photographic emulsionsupports. Typical supports include cellulose ester film, polyvinylacetalfilm, polystyrene film, polyethylene terephthalate film and relatedfilms or resinous materials, as well as paper and glass. It is alsopossible to employ paper coated with α-olefin polymers e.g. paper coatedwith polyethylene, polypropylene, ethylene-butylene copolymers, etc.

For the production of photographic colour images according to thepresent invention an exposed silver halide emulsion layer is developedwith an aromatic primary amino developing substance in the presence of acolour coupler according to the present invention. All colour developingagents capable of forming azomethine dyes can be utilised as developers.Suitable developing agents are aromatic compounds such as p-phenylenediamine and derivatives for example N,N-diethyl-p-phenylene diamine,N-butyl-N-sulphobutyl-p-phenylene diamine,N,N-diethyl-N'-sulphomethyl-p-phenylene diamine,N,N-diethyl-N'-carboxymethyl-p-phenylene diamine,2-amino-5-diethylaminotoluene,4-amino-N-ethyl-N(β-methanesulphonamido-ethyl)-m-toluidine,N-hydroxyethyl-N-ethyl-p-phenyle diamine, etc.

The following examples illustrate the present invention.

EXAMPLE 1

A dispersion in aqueous gelatin of colour coupler 2 having the followingstructural formula : ##SPC1##

was prepared by dispersing a solution of 12 g of colour coupler in 30 mlof ethyl acetate, in 100 ml of 10 % aqueous gelatin comprising 1 g ofthe sodium salt of laurylbenzene sulphonate and then removing the ethylacetate by evaporation under reduced pressure.

The dispersion was admixed with a green-sensitized silver bromideemulsion comprising per kg 19.25 g of silver bromide and 77 g ofgelatin.

The emulsion was coated on a transparent film support and exposed, afterdrying, through a grey wedge for 1/20 sec. The exposed material wasdeveloped for 8 min. at 20°C in the following composition :

    N-butyl-N-ω-sulphobutyl-p-                                               phenylenediamine    6        g                                               hydroxylamine hydrochloride                                                                        4        g                                               anhydrous sodium sulphite                                                                          4        g                                               potassium carbonate  100      g                                               potassium bromide    1        g                                               water to make        1        liter.                                      

The material was then bleached and fixed in the usual way to leave amagenta wedge image having absorption maximum at 530 nm.

EXAMPLE 2

Example 1 was repeated with the only difference that development nowtook place in the following composition :

    2-amino-5-[N-ethyl-N(β-methylsul-                                         phenylamino)ethyl]      2 g                                                  anhydrous sodium sulphite                                                                              0.5 g                                                anhydrous sodium carbonate                                                                            30 g                                                  water to make            1 liter                                          

A magenta wedge image was obtained having absorption maximum at 534 nm.

EXAMPLE 3

To 50 ml of a green-sensitized silver halide emulsion as described inexample 1, 5 g of colour coupler 3 having the following structuralformula : ##SPC2##

was added from a gelatin dispersion prepared by dispersing a solution ofthe colour coupler in 15 ml of ethyl acetate and 15 g of tri-o-cresylphosphate in 50 ml of 10 % aqueous gelatin comprising 0,5 g of thesodium salt of laurylbenzene sulphonate and then removing the ethylacetate by evaporation under reduced pressure.

After coating the emulsion on a support and drying the layer, theemulsion was exposed and developed as described in examples 1 and 2 toyield magenta wedge images having absorption maxima at 528 nm and 536 nmrespectively.

After development in the following composition :

    2-amino-5-diethylaminotoluene                                                  hydrochloride           2.5 g                                                anhydrous sodium sulphite                                                                              5 g                                                  anhydrous sodium carbonate                                                                            20 g                                                  potassium bromide        2 g                                                  water to make            1 liter                                          

a magenta wedge image having absorption maximum at 534 nm was obtained.

EXAMPLE 4

17 g of colour coupler 1 having the following structural formula :##SPC3##

were dissolved in 50 g of tri-o-cresylphosphate and 50 ml of ethylacetate. The solution was dispersed in 170 ml of 10 % aqueous gelatincomprising 1.7 g of the sodium salt of laurylbenzene sulphonate,whereupon the ethyl acetate was removed by evaporation under reducedpressure.

The gelatin dispersion of colour coupler 1 was admixed with agreen-sensitized silver halide emulsion comprising per kg 30 g of silverbromide and 105 g of gelatin.

After coating, exposure and development as described in examples 1 and 2magenta wedge images were obtained having absorption maxima at 530 nmand 536 nm respectively.

EXAMPLE 5

13 g of colour coupler 4 having the following structural formula :##SPC4##

were dissolved in 36 g of tri-o-cresyl phosphate and 36 ml of ethylacetate. The solution was dispersed in 130 ml of 10 % aqueous gelatincomprising 1.3 g of the sodium salt of laurylbenzene sulphonate. Theethyl acetate was then removed by evaporation under reduced pressure.

The gelatin dispersion of colour coupler 4 was then admixed with 500 gof a green-sensitized silver bromoiodide (3 mole % of iodide) emulsioncomprising 0.115 mole of silver halide.

The emulsion was coated and exposed as described in example 1.

After development in the compositions of examples 1, 2 and 3respectively magenta wedge images were obtained having absorption maximaat 532 nm, 538 nm and 528 nm respectively.

We claim:
 1. Method of producing a magenta coloured photographic image in a photographic light-sensitive silver halide material which comprises exposing the material and developing it with an aromatic primary amino colour developing agent in the presence of a 2-pyrazolin-5-one colour coupler corresponding to the formula : ##EQU3## wherein : R₁ represents hydrogen, alkyl or aryl,R₂ represents a fluoroalkyl group X(CF₂)_(n) -- wherein X is hydrogen or fluorine and n is 1 to 10, an α-cyanoalkyl group, or a phenyl group, X represents hydrogen or a substituent that exhibits 2-equivalent character, Ar represents a phenylene group, and Y represents an alkyl group, an aryl group, a monoalkylamino group, a monoarylamino group, a dialkylamino group or an alkylarylamino group.
 2. Method according to claim 1, wherein the colour coupler is present in the light-sensitive material and is one wherein Y is or comprises an aliphatic hydrocarbon group of at least 5 C-atoms.
 3. A photographic element containing at least one silver halide emulsion layer and a 2-pyrazolin-5-one colour coupler corresponding to the formula : ##EQU4## wherein : R₁ represents hydrogen, alkyl or aryl,R₂ represents a fluoroalkyl group X(CF₂)_(n--) wherein X is hydrogen or fluorine and n is 1 to 10, an α-cyanoalkyl group, or a phenyl group, X represents hydrogen or a substituent that exhibits 2-equivalent character, Ar represents a phenylene group, and Y represents an alkyl group, an aryl group, a monoalkylamino group, a monoarylamino group, a dialkylamino group or an alkylarylamino group.
 4. The method according to claim 1 wherein Y is a monoalkylamino group.
 5. The method according to claim 1 wherein Y is a monoarylamino group.
 6. The method according to claim 1 wherein Y is a dialkylamino group.
 7. The method according to claim 1 wherein Y is an alkylarylamino group.
 8. The method according to claim 1 wherein X is a member of the group consisting of hydrogen, a halogen atom, alkylthio, arylthio, heterocyclic thio, alkoxy, aryloxy, acyloxy, sulpho, and arylazo.
 9. The photographic element according to claim 3 wherein Y is a monoalkylamino group.
 10. The photographic element according to claim 3 wherein Y is a monoarylamino group.
 11. The photographic element according to claim 3 wherein Y is a dialkylamino group.
 12. The photographic element according to claim 3 wherein Y is an alkylarylamino group.
 13. The photographic element according to claim 3 wherein X is a member of the group consisting of hydrogen, a halogen atom, alkylthio, arylthio, heterocyclic thio, alkoxy, aryloxy, acyloxy, sulpho, and arylazo. 